Oracle 11g Release 2

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create table t(col1 varchar2(10))
insert into t
select 'a,b,c,d' from dual 
1 rows affected

with data
  as (select ','||col1||',' as col1
       from t
      )
 select substr(col1
              ,instr(col1,',',1,level)+1
              ,instr(col1,',',1,level+1)
               -
               instr(col1,',',1,level)
               -1
               ) as col_values
        ,level 
   from data
connect by level<=length(col1)-length(replace(col1,','))-1
order by 2


COL_VALUES
LEVEL


a
1

b
2

c
3

d
4


select instr(',abcd,d,e,',',',1,1)
       ,substr(',abcd,d,e,'
              ,instr(',abcd,d,e,',',',1,1)
              ,instr(',abcd,d,e,',',',1,2)
              -instr(',abcd,d,e,',',',1,1)
              ) 
  from dual


INSTR(',ABCD,D,E,',',',1,1)
SUBSTR(',ABCD,D,E,',INSTR(',ABCD,D,E,',',',1,1),INSTR(',ABCD,D,E,',',',1,2)-INSTR(',ABCD,D,E,',',',1,1))


1
,abcd